UV curing speeds up Smart Motorway drain rehab

A UK company has dramatically cut the time it takes to rehabilitate motorway drainage pipes by using a curing method that also produces a stronger finished product than the traditional method.

Sapphire Utility Solutions said it used a technique originally developed for the wastewater sector on an all lane running Smart Motorway project on the M6.

It re-lined pipes using an ultra-violet (UV) light curing method that it said is twice as fast as the traditional hot water/steam method and creates a finished product more than five times stronger.

Technical and innovation manager Stuart Ashton said: ‘Cure in place methods are much faster than dig and replace, and the UV curing method offers further considerable advantages over those that involve water.

‘The speed with which we are able to fit an extremely robust and reliable lining is obviously a major advantage. However, there are huge environmental benefits because the new method does not produce contaminated curing water and does not involve large fossil fuel burning boilers and plant.’

Sapphire Utility Solutions is working as a sub-contractor for a Carillion Kier Joint Venture, which is one of three delivery partners for the Highways England Smart Motorway.

Under all lane running, which will operate for 30km between junctions 16 and 19 of the M6, the former hard shoulder will be subjected to much higher levels of traffic, so the underlying drains are being fitted with a fibreglass lining that is both rigid and extremely strong.

Sapphire’s work on the project began in February and Mr Ashton said it could be completed as early as October. He said if pipeline replacement had been carried out instead of re-lining, the project would have taken an extra year, delaying the benefits of all lane running and significantly extending traffic disruption.

The liner employed by Sapphire Utility Solutions consists of fibreglass, a polyester resin and a UV actuator. After exposing the actuator to UV light, an exothermic reaction causes the resin to set hard.

The liner is therefore delivered to site in lengths of up to 300 metres inside a bag that protects it from natural UV light. The liner is drawn into the pipe with the bag still in place and inflated to fit tightly inside the original pipe.

A UV light train is then pulled though the liner to initiate the curing process. The curing time depends on the diameter of the pipe but a typical 300mm pipe cures at a rate of 1.5 metres per minute. The fully cured lining provides a rigid, durable pipe with a design life of 70 years. Once the lining is in place Sapphire employs robotic cutting techniques to open lateral connections.

Mr Ashton said: ‘Considering the major advantages of this technique we believe that it will become the preferred method on future projects.’

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